The emgm package

EMGM is a general-purpose library for generic programming with type classes.

The design is based on the idea of modeling algebraic datatypes as
sum-of-product structures. Many datatypes can be modeled this way, and
because they all share a common structure, we can write generic functions that
work on this structure.

The primary features of the library are:

A platform for building generic functions and adding support for user-defined datatypes.

EMGM includes an important collection of datatypes (e.g. sum, product, and
unit) and type classes (e.g. Generic and Rep). Everything you need for
your own generic functions or datatypes can be found here.

Many useful generic functions.

These provide a wide range of functionality. For example, there is crush
(Generics.EMGM.Functions.Crush), a generalization of the foldl/foldr
functions, that allows you to flexibly extract the elements of a polymorphic
container. Now, you can do many of the operations with your container that
were previously only available for lists.

Different generic functions work with different kinds of types as well. For
example, collect (Generics.EMGM.Functions.Collect) works with any fully
applied type while bimap (Generics.EMGM.Functions.Map) only works with
bifunctor types such as Either or (,) (pairs).

Support for standard and user-defined datatypes.

EMGM provides full support for standard types such as [] (lists), tuples,
and Maybe as well as many types you define in your own code. Using the
Template Haskell functions provided in Generics.EMGM.Derive, it is very
simple to add support for using generic functions with your datatype

Flags

Don't build the library. This is useful for speeding up
the modify-build-test loop. With "-ftest" (only), the
build command will build both the library and the test
executable. With "-ftest -fnolib", the build command
builds only the test executable.

Disabled

Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info